1. Technical Field of the Invention
The present invention relates to unique luminophores comprising doped tantalates of yttrium, lutetium or gadolinium, to luminescent compositions comprised thereof, and to low-voltage luminescing electronic devices incorporating such luminophores/luminescent compositions.
2. Description of the Prior Art
It is known to the electronics arts that cathode ray tubes operate using a substantial level of energy, on the order of 30,000 V. It would be desirable, however, to employ lower levels of energy for such applications, namely, on the order of from 200 to 800 V. This is the case in respect of field emission displays (FED). Such equipment comprises metallic microdots which emit the low-energy electrons to excite a luminophorous material which is disposed on the display screen.
That luminophorous material must have two essential properties.
It must first have adequate optical characteristics, associated with its luminescence properties, and it must emit effectively in the desired color range.
The second required property is electrical conductivity. The material must indeed dissipate electrical charges when used for the aforesaid application.
Few materials exist which combine these two properties to an adequate degree. Indeed, luminous effectiveness of the material decreases with excitation potential. In addition, there is a minimum excitation potential (Vamin), below which the material no longer exhibits conductivity. Given the desirability to operate at a potential range which is as low as possible, on the order of from 200 to 800 V as indicated above, serious need continues to exist for materials which have the lowest possible Vamin while retaining adequate luminous effectiveness.